I highly recommend this book for serious history buffs who read a lot of nonfiction and enjoy a high level of detail about the many people who played a part in historical events. I also recommend it for more casual readers of nonfiction who have a strong interest in this subject and time period. I say that with the warning that there are a lot of people involved, and it can be difficult to keep track of them and their roles and backgrounds.
Kertzer is a meticulous researcher with expert knowledge of Italian history. The book gives much more extensive coverage of people and events than the title implies. At times it's fascinating, at other times it's a bit too thorough, but it's always extremely well written and documented. There is a wealth of notes at the back of the book, as well as numerous photographs throughout the book that greatly enhanced my enjoyment and understanding of the material.
I found it especially interesting that Pius XI and Mussolini shared some personality traits. Of course, Mussolini's manifested in a more extreme fashion, but both men were ruthless and narcissistic.